The present invention relates to an optical disk apparatus for recording and/or reproducing information signal onto and from at least one side of a double-sided optical disk.
FIG. 12 schematically shows the construction of a conventional optical disk player for reproducing information from both sides, i.e., side A and side B, of an optical disk (referred to simply as "disk", hereinafter). Referring to FIG. 12, signals representing information are recorded both in the side A and the side B of a disk 100. During reproduction from the side A, an optical block 102 carrying an optical pickup 101 for reproducing signals moves in the radial direction of the disk (direction perpendicular to the plane of sheet of the drawing), while being guided by a guide shaft 104 provided on a main base member 103 and under a position control performed by a cooperation between a rotatable roller 105 on the optical block and a roller control member 106 provided on the main base member 103. The power for radially driving the optical block 102 is produced by a motor carried by the optical block 102. The power is transmitted through a plurality of reduction gears (not shown) to a drive gear 107 which meshes with teeth on a rack member 108 fixed to the main base member 103. That is, the optical block 102 propels itself. On the other hand, during reproduction from the side B, an optical block 102 moves in the radial direction of the disk while being guided and restricted by a guide shaft 110 provided on a sub-base member 109 fixed to the main base member 103 and by a roller control member 111.
This known arrangement suffers from the following disadvantage. Namely, since the optical block 102 during reproduction from the side B is guided by the guide shaft which is carried by the sub-base member 102, the positional precision of the optical block 102 during reproduction from the side B tends to be impaired due to, for example, dimensional error or warp of the sub-base itself or error of mounting of the sub-base member 109 on the main base member 103 on which the guide shaft for the reproduction from the side A is mounted. This often results in a serious difference between the reproducing performance for the side A and that for the side B. Furthermore, since the optical block 102 carries a self-propelling mechanism, the size of the optical block 102 and, hence, the size of the whole apparatus are increased. In addition, an increase in the motor speed for the purpose of attaining a higher moving speed of the optical block 102 raises the levels of noise and vibration, with the result that the reproducing performance, as well as the quality of operation, is impaired.